PROJECTSUMMARY Preventing overweight in preschoolers may be an effective way to reduce the lifetime risk of obesity. Though adequate,qualitysleepisincreasinglyrecognizedasessentialformaintainingahealthyweight,theriskfactors for insufficient sleep in preschoolers are poorly understood. While media use has been associated with insufficient sleep in preschoolers, most studies are limited because of unmeasured confounding related to householdchaosandasolefocusontotalmediausequantityorbedroommediausewithoutconsideringmedia content.Furthermore,insufficientsleeplikelyleadstoovereatinginadults,yetfewstudieshaveconsideredthat effectinpreschoolers.Mylongtermgoalsaretobecomeanexpertinhowpreschoolersengagewithmediaand how media use impacts sleep and obesity risk, while emphasizing the use of wearable devices to objectively measuremediauseandsleep.Myobjectivesforthismentoredresearchscientistdevelopmentawardarethus tobecomeanexpertin1)conductingprospectiveresearchstudiesonobesitypreventioninearlychildhood,2) mediausebehaviorsinpreschoolers,3)usingwearabledevicestoobjectivelymeasuremediauseandsleepin preschoolers, and 4) mastering advanced statistical methodology needed for establishing causal inference in health behavior research. I will complete my training with coursework, participation in the plenary sessions, workshopsandshort-coursesattargetedscientificmeetings,andthroughthecompletionofanovel,prospective research study to examine the causal relationships between media use, sleep, overeating and weight gain in preschoolers. My research is particularly novel because I consider how the content of media preschoolers engagewithmodifiestherelationshipbetweenmediauseandsleep.Myinnovativeresearchdesignaccounts forhouseholdchaoswithavalidatedmeasure,includesthenovelapplicationofavalid,wearableaudiorecording devicetoobjectivelymeasuremediaexposure,andincludesalaboratory-basedassessmentofovereating(i.e., eating in the absence of hunger) to define the association of nighttime sleep on subsequent overeating. Importantly,myprogramwillbeconductedundertheguidanceofanexpertmentorshipteamthatconsistsofa pediatricianandbehavioralepidemiologist(Dr.Sargent),anepidemiologistinearlychildhealth(Dr.Karagas),a behavioral researcher in early childhood obesity prevention (Dr. Benjamin Neelon), and a statistician in behavioralresearch(Dr.O?Malley),aswellasthreeadvisorswithspecializedtraininginsleepandchildeating behaviors.InYear5IwillsubmitanR01proposalforaprospectivestudyproperlypoweredtodefinethecausal relationshipsbetweenmediauseandexcessweightgainwhileconsideringmediatingandmoderatingfactors. Thislineofresearchwillsubstantiallyadvancetheunderstandingforhowpreschoolersengagewithmediaand how that use impacts sleep, and ultimately, obesity risk. With my strong quantitative background and documentedsuccessasanearlyinvestigator,IhavenodoubtIcanleadthisexcitingandnovelareaofresearch.